Ethernet controllers have evolved from the original network card type systems that provide network speeds of 2 Mb/s to 10 Mb/s, 100 Mb/s and up to current speeds of 1,000 Mb/s. The 2 Mb/s network interface cards have all but disappeared. Most network interface systems, or network interface cards (NIC), currently provide for three higher speeds, 10/100/1,0000 Mb/s. These are usually referred to as a 10 base T, 100 base T, and 1,000 base T, the “T” referring to a twisted pair physical media interface, other interfaces providing for the connection to optical fibers and the like. Each of the various configurations, at whatever speed, includes on an integrated circuit, a media side circuit or media access controller, the MAC, and a physical side circuit or physical layer, the PHY. The NIC is operable to provide timing and encoding/decoding for receiving data and transmitting data. Typically, when data is transmitted over the physical transmission line, such as an RJ 45 twisted wire cable, data will be received by the NIC from a processing system and this data is stored in a FIFO of some sort, encoded for transmission and then transmitted. For received data, the opposite operation occurs. These are well known circuits and fairly complex. At higher speeds, the core processing circuitry basically requires a digital signal processing (DSP) capability. Further, each network card will have associated therewith a unique address, such that it is unique to all other address cards and can be disposed on any network regardless of what other cards are disposed on the network. This is for the purpose of uniquely identifying any network device that is disposed on the network apart from other network cards. To facilitate this, a large block of numbers was originally created for the ethernet by a centralized standards body, which large block of numbers is considered to be an inexhaustible number.
The network interface cards further include an interrupt output and an interrupt register for providing an indication of interrupt problems between a network interface controller and an attached MCU. When an interrupt condition occurs, this information related to the interrupt condition is stored within an interrupt register of the NIC card, and an interrupt signal is sent from the NIC card to the attached MCU. Two conditions which generate an interrupt from the NIC card to the attached MCU are a loss of lock of the phase locked loop within the network interface card and the occurrence of a brownout condition within the network interface card. Brownout occurs when the voltage of the network interface card drops below 3.1 V. While each of these conditions will cause an interrupt to be generated from the network interface card to the attached MCU, during each of these conditions, the MCU is unable to communicate with the network interface card. Thus, while an interrupt will be received, there will be no way for the MCU to determine the cause of the interrupt, since the MCU will be unable to communicate with the network interface card. Thus, some manner for providing an indication to an MCU from an attached network interface card that does not require the MCU to communicate with the interrupt register of the network interface card is desired.